Antenna



ANTENNA K. T. CRAMNER Filed Feb. l0, 1964 Nov. 15, 1966 United States Patent() 3,286,269 ANTENNA l Karl Torbirn Cramner, 11 Valkyriavagen, Djursholm, Sweden Filed Feb. 10, 1964, Ser. No. 343,711 Claims priority, lapplication Sweden, Feb 28, 1963,

6 Claims. (Cl. 343-830) This invention relates to a quarter-wave antenna of the ground surface type and refers more particularly to a quarter wave antenna of glass fiber construction with an extremely wide band. f f It is very desirable to use antennaswitha wide band for certainy radio communication ranges.' i By` way of example, a standing quarter wave vantenna 'with suitably constructed ground surface elements is used when a direc= tional effect is not required, but the antenna must have a circular wave lt'zharacteristic in thehorizonta'l plane vwith a large opening angle yin the vertical plane. "The band width of antennasV of this type canv be increased by using sender elements .and ground surface elements having 4the greatest possible diameters.v The-sizeV of these diameters is" limited, however, partly by the fact that the ratio between the length and the diameter of the elementsH must not ex# ceed a certain value, and partly because the wind resistance land the weight may become too great.` An object of the present invention is ready Within a permissible range.

Other objects of the present invention will become apr' ting form a coaxial resonator the inner conduit of which v is connected to the ground surface of the antenna, while' its outer conduit is, connected to the feed pointof the metal netting; a coaxial antenna cable has an inner conduit connected to the feed point of the metal netting and an outer conduit connected to that part of the metal tube which is directed toward the feed point.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawing showing, by way of example, a preferred embodiment of the inventive idea.

In the drawing:

FIGURE l is a vertical section through an antenna constructed in accordance with the principles of the present invention.

FIGURE 2 shows a part of the antenna in cross section on an enlarged scale.

The antenna shown in the drawing is mounted upon a support consisting of a metal pipe 10 the upper end of which is provided with a collar 12. A round metal disc 14 is xed upon the collar 12; a surface of the disc 14 extends conically outwardly so as to facilitate the attachment of a number of ground surface elements 16. The elements 16 are screwed into the disc 14 and can be easily removed and exchanged, so as to facilitate the transport-ation, assemblage and servicing of the antenna, as well as the changing of its wave length range. The elements 16 consist preferably of metal tubes closed on all sides, and are fgalvanically connected with the grounded support 10.

The upper side of the disc 14 has a round centrally located recess 18. A bottom plate 20 is mounted in the recess 18 and is fixed to the disc 14 by screws.

te 'provide means' for further increasing the band width of antennas the di ameter of the elements of whichhas been increased al-H lCC A tubular thin-walled metal cylinder 22 has the lower end thereof secured to the outer surfaces of the plate `2.0 preferably by welding or hard soldering and is abutting the adjacent surfaces of the recess 18 of the plate 14. The upper end of the cylinder 22 is Igalvanically connected with a 'sender or receiver element 24 of the antenna.

As best shown in FIG. 2, the element 24 consists of a rigid body having an inner portion 26 made of a plastic material and carrying a metal netting 28 which in turn is covered by aplastic .layer 30.

Dosed polyester resin mixed with and reinforced by glass fibers was found t-obe best suited as the plastic material.

The inner member 26,` the metal netting 28 and the outer I'plastic layer 30 are rmly united through the meshes of the netting 28 and thus constitute a single homogeneous body 24 of plastic material lwithin which the metal netting 28'is embedded.

The element l24 comprises a flat round top portion 32 and an integral cylindrical portion 34 joining the circumference of the top 32. The lower end of the element 24 extends into an insulator 36 having the shape of an :annular plat with an upwardly extending circumferential flange 38. The plate36 can be made of cast resin or other suitable material. The flange 38 extends as a protective 'cover over the lower end of the element 24. The inner circumferential surfaces of the insulator 36 are firmly conne'ctedwtih the `cylinder 22.

#1A coaxial cable v40 extends through the pipe 10 and through openings provided in the disc 14 and the plate 20. The cable 40 passes through an opening in the lower portion of the cylinder 22 and the cylindrical outer con duit of the cable 40 is galvanically connected therein to the cylinder 22. The inner conduit of the cable 40 is connected at 42 to the lower end of the metal netting 28.

Thus the coaxial cable 40 connects the metal netting 28 with a sender or receiver (not shown) In operation,.the element 24 serves electrically as a quarter wave antenna which is fed lat its base point 42 and which has a wide band width due to its very large diameter relatively to its length. The band width is further increased by the fact that the hollow space between the cylinder 22 andthe element 24 acts as a coaxial oscillating circuit or a coaxial resonator, the circuit capacity of which can be considered as being shifted to the portion of the element 24 at the feed point 42 and to the portion of the cylinder 22 located opposite this feed point; this assumption leaves 4out of consideration the fact that actually the circuit capacity is distributed along the cylindrical walls of -cylinder 22 and element 24 which face the hollow space therebetween, while the circuit inductance is formed by the conducting members in the cylindrical portion 34 and the upper portion 32 of the element 24 and the outer surface of the cylinder 22. The coaxial circuit constituted by the cylinder 22 and the element 24 is connected in parallel with the feed point of the antenna, namely, the innei conductor (cylinder 22) of the coaxial circuit is connected with the ground surface elements, and the outer conductor (metal netting 28) of the coaxial circuit is connected with the feed point 42 of the netting 28 constituting a part of the element 24. This parallel connection of the coaxial circuit with the element 24 causes a further drop or lowering of the resonance curve of the antenna, i.e., an increase in the band width. The coaxial circuit can be also considered as representing a short circuited quarter Wave tap conduit with ysmall impedance due to large circuit capacity and comparatively small circuit iimpedance. Due to this arrangement the element 24 of the antenna has a double function, namely, its outer surface cooperates electromagnetical'ly with the space, while its inner surface constitutes a part of a coaxial resonator.

In addition to the great band width, this arrangement results in further advantages, namely, the antennacan be constructed compactly and its construction is simple; furthermore, the radiation element is galvanically grounded. The construction of the radiation element illustrated in FIG. 2, namely, the combination of the metal netting and the plastic layers, makes possible a further diminution of the structural length of the element 24, due to the di-j electric constant of the plastic material. Finally, the construction of the present invention' has the advantage'that the radiation element is of light weight and yet stable and secure from corrosion, since the metal netting is embedded in plastic material. Furthermore, the diameter of the radiation element can be adapted to a size which is best suited from the electrical point of view, which is not possible with commercially available metal tubes or metal rods.

It is apparent that the example described above has been given solely by way of illustration and not by way of limitation and that it is subject tomany variationsand modifications Within the lscope of the present invention. All such variations and modications are to be included within the scope ofthe present invention.

What is claimed is: H

1. A quarter wave antenna of the ground surface type,

comprising a radiation element having a plastic cylindricalA portion, an integral substantially at top portion closing,

mentioned outer conduit being electrically connected with.

said metal cylinder at a location facing said feed point.

2. An antenna, in accordance with claim 1, wherein said metal netting is embedded in said plastic portions.

3. An antenna in 4accordance with claim'l, wherein the top portion of said metal netting is galvanically connected with said metal cylinder. l

4. A quater wave antenna of the ground surface type,

comprising a radiation element having a plastic cylindrical portion;t an integral substantially flat top portion closing saidcylindrical portion and a metal netting carriedby s aid portions and having a feed point, a thin-walled metal cylinder located within said element and spaced from the cylindrical portion thereof, whereby said metal cylinder and said metal netting constitute respectively the inner and outer conduits of a coaxial resonator, a plate-shaped insulator having circumferential surfaces firmly connected lwith a lower end' of said plastic cylindrical portion, said insulator being firmly connected with said metal cylinder, and a .coaxial antenna cable having an inner conduit and an outer conduit, the last-mentioned inner conduit being electrically connected with said metal netting at said feed point, the last-mentioned outer conduit being electrically connected with said metal cylinder at a location facing said feed point.

5. A quarter wave antenna of the ground surface type,

comprising a radiation element having a plastic-cylindrical portion," an integral substantially llat topv portion closing 20.

said cylindrical portion, Vand. a metal netting carried by said portionsand having-'aV feed point, a thin-walled metal cylinder located within; 4said element andwspaced from the cylindrical portion thereof, whereby said metal cylinder and. said metal netting constitute respectively the innerand outer conduits of a coaxial resonator,a plate-shaped.

insulator; having circumferential surfaces rmly connected with y.a lower eind of said plastic cylindrical portion, and a disc constituting the ground surface ofthe antenna, said insulator being xed to said disc, and a coaxial antenna cable having. an inner conduit and an outer conduit, the last-mentioned inner conduit being electrically connected withy said metal netting at said feed point, the last-mentioned .outer conduit being electrically connected with said n metal cylinderv at alocation facing said feed point. 35

6. Anantenna in accordance with claim 5, wherein said plastic cylindrical portion, said insulator and said metal cylinder constitute a unit fixed to said disc.

References Cited bythe Examiner UNITED STATES PATENTS `HERMAN KARL SAALBCH, Primary Examiner.

ELI LIEBERMAN, Examiner. P. L. GENSLER, Assistant Examiner. 

1. A QUARTER WAVE ANTENNA OF THE GROUND SURFACE TYPE, COMPRISING A RADIATION ELEMENT HAVING A PLASTIC CYLINDRICAL PORTION, AN INTEGRAL SUBSTANTIALLY FLAT TOP PORTION CLOSING SAID CYLINDRICAL PORTION AND A METAL NETTING CARRIED BY SAID PORTIONS AND HAVING A FEED POINT, A THIN-WALLED METAL CYLINDER LOCATED WITHIN SAID ELEMENT AND SPACED FROM THE CYLINDRICAL PORTION THEREOF, WHEREBY SAID METAL CYLINDER AND SAID METAL NETTING CONSTITUTE RESPECTIVELY THE INNER AND OUTER CONDUITS OF A COAXIAL RESONATOR, GROUNDED SUPPORTING MEANS CARRYING SAID ELEMENT, SAID METAL CYLINDER BEING 